I'd say RPG's and SRPGs. There are a lot of them.

I'd say puzzle, but only a bit more than platformers and RPGs.

RPG. Had a hard time picking between that and Adventure though. Trace Memory, Hotel Dusk, and Pheonix Wright are amazing games. But they can't top TWEWY or Chrono Trigger. :(

I'm glad I voted platformer. Those RPGS are getting all the love. Poor SRPGs, action, adventure, action adventure, rhythm, and shooters... Perhaps i should have split RPG up into turn based and live. 

If you mean the most games, couldn't tell you. But the "strongest" as in has a high amount of quality games it is certainly RPGs. There are tons of amazing RPGs on the DS.

I had to go with SRPG.  It is RPG but with an S.  That makes it better :P  Tough choice, very close with RPG, then Simulation (like Harvest Moon).